When a workpiece is to be machined by a working machine, it is necessary to bring the coordinate system of the workpiece mounted on a machine platen into line with the coordinate system of the working machine, and therefore the workpiece is usually fine-adjusted (centering operation) on the machine platen. Frequently used for supporting the workpiece is a fluid-pressure support system that utilizes a slide surface of a static pressure pocket. This fluid-pressure support system supports a workpiece by a pressurized fluid (hydraulic oil) while floating the same, and therefore achieves relatively easy moving operation of the workpiece thanks to low friction force caused by the movement in the horizontal direction.
An example of the structure of the fluid-pressure support system is illustrated in FIG. 16. In this example, the system is so structured to have an object to be supported (workpiece or mounting table for mounting the workpiece) 71, slide surfaces 73, 74 formed respectively on the oppositely facing sides of the object 71 and a support member 72 for supporting the object 71, a pressurized fluid being discharged from a fluid supplying unit 77 and introduced via a throttle 78 into a ring groove 76 formed in the slide surface 74 on the side of the support member 72, and a static pressure pocket 75 formed between the slide surfaces 73, 74 in the area surrounded by the ring groove 76.
However, the static pressure pocket 75 which is exposed to the atmosphere causes flowing-out of the pressurized fluid therefrom. Therefore, pressurized fluid must be constantly supplied and a recovering mechanism for recovering the fluid which tends to be increased in size. This causes a disadvantage in that the entire size of the system is increased and running costs are also increased. In addition, the static pressure pocket 75 exposed to the atmosphere produces a pressure of generally only about 0.5 to 1 MPa to the slide surfaces, and therefore is likely to cause insufficient surface pressure for a heavy workpiece. Meanwhile, there is caused a surface pressure of only about 0.2 to 0.3 MPa to a usual dynamic pressure slide surface.
For example, in order to easily position a heavy workpiece, such as a workpiece having a weight of more than 10 tons, with respect to a working machine, a slide surface pressure of about 25 MPa (ultra high fluid pressure) is required. However, a fluid-pressure support system utilizing a slide surface of the conventional static pressure pocket as described above is highly unlikely to be able to ensure such a high surface pressure. For ensuring such a high surface pressure, a structure for allowing a fluid pressure pocket to be formed between the slide surfaces while allowing the same to be sealed from the atmosphere is required, but for this, a nonconventional, rigid fluid sealing mechanism that is capable of ensuring high sealability must be provided.
The present invention has been conceived in consideration of the above circumstances. It is an object of the present invention to provide a fluid sealing mechanism with a good sealability so as to be able to ensure a high surface pressure between the slide surfaces of the object and the support member, and a heavy load support system that is equipped with the fluid sealing mechanism, as well as being simple in structure and compact in size.
It is desirable that such a heavy load support system can as well perform positional adjustment of an object to be supported (workpiece or mounting table for supporting the workpiece) in the vertical position. Thus, it is another object of the present invention to achieve this purpose.